Schematic of Reverted GearTrain. 
A 'Reverted Gear Train' has:
It is a Compound Gear with, two GearsPairs, and a special condition that makes the total number of teeth of the first gearpair equals the number of teeth of the secondgearpair, when the module is the same. The image to the left shows a schematic of a Reverted GearTrain. There is more than one gearpair, two shafts, and the input and output shafts are coaxial. Therefore, it agrees the definition of the Reverted Gear Train. See Also: Simple GearPair, Simple GearTrains, Planetary GearTrains

Start with a GearPair with an External Mesh see Option 1 Step 14.1 Here, the numberofteeth are: T1=30, T2=70. The Gear Ratio is T1/T2 = 2.5 The total numberofteeth is 100T. 
We use the Point to add a PinJoint at the left end of the Line in the BasePart two times 


Add the second GearPair.
This dimension is already a 'drivendimension'. 

Edit the GearPair 2 Edit the Number of Teeth: Gear 1 = 20 Gear 2 = 80 Video See Video to the left to see the gear reduction of the GearPair. The Gear Reduction is : 30*20 : 70*80 = 3: 28 